Enhanced uplink (EU) is one of the major features in third generation partnership project (3GPP) frequency division duplex (FDD) systems. EU offers a peak data rate of 5.76 Mbps. Several downlink physical channels are provided to support EU transmissions. One of the downlink channels is the E-AGCH.
FIG. 1 is a block diagram of a conventional wireless communication system 100 which supports EU. The system 100 includes a WTRU 102, a Node-B 104 and a radio network controller (RNC) 106. The RNC 106 controls overall E-DCH operation by configuring E-DCH parameters for the Node-B 104 and the WTRU 102, such as an initial transmit power level, maximum allowed transmit power or available channel resources per Node-B. Between the WTRU 102 and the Node-B 104, an E-DCH 108, an E-DCH dedicated physical control channel (E-DPCCH) 110, an E-AGCH 112, an E-DCH relative grant channel (E-RGCH) 114 and an E-DCH hybrid automatic repeat request (H-ARQ) indicator channel (E-HICH) 116 are established for supporting E-DCH operations.
For E-DCH transmissions, the WTRU 102 sends scheduling requests, (also known as rate requests), for the logical channels which a radio resource control (RRC) determines that reporting is needed to be made to the Node-B 104 via the E-DCH 108. The scheduling requests are transmitted in the form of scheduling information and happy bit. The happy bit is transmitted via the E-DPCCH 110 whenever the E-DPCCH 110 is transmitted. The Node-B 104 sends a scheduling grant to the WTRU 102 via the E-AGCH 112 or the E-RGCH 114. After E-DCH radio resources are allocated for the WTRU 102, the WTRU 102 transmits data via the E-DCH 108. In response to the E-DCH transmissions, the Node-B 104 sends an acknowledgement (ACK) or a non-acknowledgement (NACK) message for H-ARQ operation via the E-HICH 116.
The E-AGCH 112 is a very important channel for performing fast scheduling in the EU. The E-AGCH 112 carries the scheduling grant in the form of a maximum power ratio for the WTRU 102. The maximum power ratio is given by the power ratio of the E-DCH dedicated physical data channel (E-DPDCH) over the dedicated physical control channel (DPCCH) (not shown in FIG. 1). In addition, the E-AGCH 112 also carries an activation flag that is used to activate or deactivate H-ARQ processes, indicating activation or deactivation of either single or all H-ARQ processes.
The E-AGCH 112 is transmitted with an E-DCH radio network temporary identifier (E-RNTI). Under the current 3GPP standards, two E-RNTIs may be configured for the WTRU 102 at a time. One is a primary E-RNTI and the other is a secondary E-RNTI. Only one E-RNTI may be transmitted at a time. The WTRU 102 should monitor both E-RNTIs if configured. Decoding of the E-AGCH 112 has to be performed for both E-RNTIs if configured. The success or failure of the decoding of the E-AGCH 112 significantly affects the performance of the EU. Therefore, it is desirable to provide a reliable method for decoding the E-AGCH 112.